Extraction of metals from ore or the like.



UNITED STATES PATENT CFFIoE.

BERTRAM HUNT, SAN FRANCISCO, CALIFORNIA.

EXTRACTION OF METALS FROM ORE OR THE LIKE.

SPECIFICATION forming part of Letters Patent No. 699,108, dated April29, 1902. Application filed July 12,1901. Serial No. 68,061. (Nospecimens.)

T at whom it may concern:

Be it known that I, BERTRAM HUNT, a na tive of Scotland and a Britishsubject, residing in the city and county of San Francisco,

State of California,have invented an Improvement in the Extraction ofMetals from Ores or the Like; and I hereby declare the following to be afull, clear, and exact description of the same.

This invention has for its object the treatment of ores containing gold,silver, copper, 'zinc, nickel, &c., in a single operation; and it isespecially applicable to such ores when containing a relatively smallamount of copper, time, or base metals, which prevents their successfultreatment by the'ordinary cyanid process. 1

My invention and processconsists in leaching the ores or tailings with asolution con taining a quantity of free ammonia and a quantity of acyanid.

It is known that the double cyanids of zinc and potassium and of copperand potassium ave a solvent power for gold and that the cyanids of gold,silver, and copper and other base metals are soluble in ammonia.

I have discovered that on leaching some ores containing gold, silver,and copper with a solution containing two to three per cent. of ammoniaand two pounds of potassium cyahid per ton of ore that the gold, silver,and copper were extracted.

It is not possible to give exact proportions of the ammonia andcyanidrequired, as they must be varied to suit orestof varying composition. I

In the case of a low-grade material containing gold and silver with twoor three tenths of one percent. of copper (which is sufficient toprevent its treatment bythe ordinary cyanid process) I would leach witha solution containing one pound or more of potassium or other cyanid tothe ton, this depending upon the richness of the ore, and two or threepounds of ammonia to the ton. 1

Instead of using ammonium hydrate I may use a salt of ammonia, such asthe sulfate, and mix lime or other alkali with the ore under treatment.

In some cases a small amount of an oxidizing agent may be used with theammonia and a cyanid. If the material treated contains any ferrous salt,it should be removed by adding the ammonia solution and either anoxidizing agent, or it may be oxidized by the air, which prevents itsconversion into a ferrocyanid. This should be done previous to theaddition of the cyanid.

In some cases mercuric cyanid may be used instead of. an alkalinecyanid. In the case of richer material containing a considerableproportion of copper a larger quantity of ammonia would be required.Theoretically sixty three parts of copper require thirty-four parts ofammonia to dissolve it; but in practice I wouldalways use an excess ofammonia.

In the case of tailings or other low-grade material requiring the use ofvery dilute solutions I would leach in ordinary vats fitted withsuitable filter-bottoms.

In some cases agitation can be employed with advantages, and in suchcases I would prefer to use a barrel fitted with an internal filter. Thegold and silver maybe recovered from the solution by electrolysis,precipitation by zinc, or other well known process, and the copper orother base metals may be recovered by boiling ofi the ammonia and soprecipitating the metals or by other wellknown methods.

In some cases the solution can be used repeatedly, being brought up tothe required strength at each treatment by the addition of the requiredamounts of cyanid and ammonia. In other cases the ammonia may berecovered by distillation and a portion of the cyanid maybe recovered ascyanid of copper or zinc or other metallic cyanid by precipita tion witha metallic salt or its neutralization by the addition of an acid.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, is-

1. The process of extracting metals from ores or materials with asolution in which a cyanid salt and free ammonia are present and addingto the solution an oxidizing agent.

3. The process of extracting metals from 5' ores, consisting in leachingthe pulverized material with a solution containing a oyanid compound, asalt of ammonia, and an alkali capable of liberating ammonia from thesalt.

4. The process of extracting metals from I0 ores, consisting in leachingthe pulverized material with a solution containing free ammonia and acyanid salt, and afterward recovering the metal by precipitation.

In witness whereof I have hereunto set my hand.

BERTRAM HUNT.

Witnesses:

GEO. H. STRONG, S. H. NOURSE.

